MicroRNAs (miRNAs) and their regulatory functions in anthocyanin, carotenoid, and chlorophyll accumulation have been extensively characterized in many plant species. However, the miRNA regulatory mechanism in betalain biosynthesis remains mostly unknown. In this study, 126 conserved miRNAs and 41 novel miRNAs were first isolated from Hylocereus monacanthus, among which 95 conserved miRNAs belonged to 53 miRNA families. Thirty-four candidate miRNAs related to betalain biosynthesis were differentially expressed. The expression patterns of those differential expressed miRNAs were analyzed in various pitaya tissues by RT-qPCR. A significantly negative correlation was detected between the expression levels of half those miRNAs and corresponding target genes. Target genes of miRNAs i.e. Hmo-miR157b-HmSPL6-like, Hmo-miR160a-Hpcyt P450-like3, Hmo-miR6020-HmCYP71A8-like, Hmo-novel-2-HmCYP83B1-like, Hmo-novel-15-HmTPST-like, Hmo-miR828a-HmTT2-like, Hmo-miR858-HmMYB12-like, Hmo-miR858-HmMYBC1-like and Hmo-miR858-HmMYB2-like were verified by 5′RACE and transient expression system in tobacco. Hmo-miR157b, Hmo-miR160a, Hmo-miR6020 Hmo-novel-2, Hmo-novel-15, Hmo-miR828a and Hmo-miR858 play important roles in pitaya fruit coloration and betalain accumulation. Our findings provide new insights into the roles of miRNAs and their target genes of regulatory functions involved in betalain biosynthesis of pitaya.

中文翻译：

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集成 sRNAome 和 RNA-Seq 分析揭示了 miRNA 对火龙果甜菜红素生物合成的影响。

MicroRNA (miRNA) 及其在花青素、类胡萝卜素和叶绿素积累中的调节功能已在许多植物物种中得到广泛表征。然而，甜菜红素生物合成中的 miRNA 调控机制仍然知之甚少。本研究首次从火龙果中分离到126个保守的miRNA和41个新的miRNA，其中95个保守的miRNA属于53个miRNA家族。34 个与甜菜红素生物合成相关的候选 miRNA 存在差异表达。通过 RT-qPCR 分析了不同火龙果组织中这些差异表达 miRNA 的表达模式。一半的 miRNA 和相应的靶基因的表达水平之间检测到显着的负相关。miRNA的靶基因即Hmo-miR157b-HmSPL6-like、Hmo-miR160a-Hpcyt P450-like3、Hmo-miR6020-HmCYP71A8-like、Hmo-novel-2-HmCYP83B1-like、Hmo-novel-15-HmTPST-like、通过烟草中的5'RACE和瞬时表达系统验证了Hmo-miR828a-HmTT2-like、Hmo-miR858-HmMYB12-like、Hmo-miR858-HmMYBC1-like和Hmo-miR858-HmMYB2-like。Hmo-miR157b、Hmo-miR160a、Hmo-miR6020 Hmo-novel-2、Hmo-novel-15、Hmo-miR828a 和 Hmo-miR858 在火龙果果实着色和甜菜红素积累中发挥重要作用。我们的研究结果为火龙果甜菜红素生物合成中涉及的 miRNA 及其调控功能的靶基因的作用提供了新的见解。